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JANUARY 2019 I FLEX007 MAGAZINE 17 image can lead designers to better signal and power integrity because you can clearly see new modes of crosstalk and return-path cur- rent directions from the folded signal paths. And of course, in the age of wireless every- thing, rigid-flex offers new options for RF and antenna geometries that are not limited to the traditional rigid PCB structures. Conclusion I've only scratched the surface, but I hope this article encourages both designers and PCB manufacturers to take the time and learn the 3D, rigid-flex, and multi-board design capabili- ties of the CAD tools they have at their disposal. Thinking and designing in three dimensions will dramatically reduce the iteration time and cycles, reveal issues earlier in the process, help you design a cost-effective, manufacturable product, and even improve your placement, routing, and signal integrity. FLEX007 Ben Jordan is senior manager of product and persona marketing for Altium. He is a computer systems and PCB engineer with over 20 years of experience in embedded systems, FPGA and PCB design. In this case, we modify the folds of the flex layer stack to accommodate passing the plastic bulkhead in the enclosure. Finally, everything fits together perfectly in the entire assembly (Figure 8). Tracing Circuit Elements Thinking and design- ing in three dimensions brings with it additional benefits. When planning for a rigid-flex PCB layout, it can sometimes be dif- ficult to think about the entire traverse of a signal connection, for example. If you're modeling the flex in MCAD only, you have no hope of clearly visu- alizing how signals and their return paths are actu- ally getting around. When you use your CAD properly, you can easily take this step when cross-probing from schematic to PCB layout. Schematic-to-PCB cross-probing gives immediate 3D and 2D visual feedback so you can precisely follow any bus, differential pair, or signal path around the folded assembly. This is shown as an example using a cross- probe of a single trace in Figure 9. Performing this step may reveal signal tra- verses that lead to important knowledge of the electrical and electromagnetic functions of the whole design. This clear, three-dimensional Figure 8: Modeling rigid-flex, rigid boards, and enclosures together in the multi-board assembly. Figure 9: Cross-probe schematic to a 3D rigid-flex PCB.